1. Field of the Invention
The present invention relates to a hydrogen filling system and a method of operating the same.
2. Description of the Related Art
A typical fuel cell vehicle carries a polymer electrolyte fuel cell. This fuel cell obtains direct-current energy by a supply of fuel gas (gas mainly containing hydrogen, e.g., hydrogen gas) to an anode-side electrode and a supply of oxidant gas (gas mainly oxygen, e.g., air) to a cathode-side electrode.
Generally, a water electrolysis device is used in producing hydrogen gas being fuel gas. The water electrolysis device employs a solid polymer electrolyte membrane (ion exchange membrane) to decompose water into hydrogen (and oxygen). An electrode catalyst layer is disposed on each of the opposite sides of the solid polymer electrolyte membrane to form an electrolysis membrane and electrode structure, and a feeder is provided to each of the opposite sides of the electrolysis membrane and electrode structure to form a unit. That is, the unit is configured substantially the same as the above-described fuel cell.
Various kinds of hydrogen filling systems for filling a fuel gas tank mounted on a fuel cell vehicle with hydrogen gas produced by a water electrolysis device are available. One such example described in Japanese Unexamined Patent Application Publication No. 2005-69332 is a hydrogen supplying station 2 for filling an on-vehicle tank 1 with hydrogen, as illustrated in FIG. 6.
The hydrogen supplying station 2 includes a tank unit 4 for storing hydrogen in a plurality of storage tanks 3 having different pressure stages Pt for stored hydrogen, a supply line 5 for use in supplying the hydrogen stored in the tank unit 4 to the on-vehicle tank 1, and a switching device 6 for switching a storage tank 3 connected to the supply line 5 to another storage tank 3.
The hydrogen supplying station 2 is configured to sequentially switch the storage tank 3 connected to the supply line 5 to the storage tanks 3 having higher pressure stages Pt by manipulating the switching device 6 as filling the on-vehicle tank 1 with hydrogen proceeds.